The theme of this final paper is to analyze the concentration of the banking sector in the Republic of Croatia. In this paper, I will first give a definition of banks, banking characteristics, describe banking activities and bank secrecy as a basis for a good relationship between the bank and the client. In order to understand the bank, primarily it is necessary to define. As for the banks, the definition of a lot, but the most common are those with the legal aspects under national legislation. Banks can be defined very simply, by functionality: The Bank is an institution that deals with the collection of funds, term deposits and financial services. The Bank is engaged in taking and raising funds because it takes funds has an obligation to that from which the funds taken. I will also say something generally about the banking sector of the Republic of Croatian and provide a theoretical overview of the index concentration.Finally, I will based on available data to calculate the value of these measures the concentration of the banking sector in the Republic of Croatia and Lika-and compare the results